A friend in Europe just told me that you are interested in “amicus curiae”
letters to explain why so many computer scientists around the world have long
been alarmed about patent trends, and that you hope to receive them by 30
April. I hope this letter reaches you in time; I could not send it by FedEx,
having no complete address.

Enclosed is a copy of a letter that I wrote to the US Patent Commissioner in
1994; I believe it is self explanatory. Also enclosed is the transcript of a
talk I gave at the Technical University of Munich in 2001, where I gave a
somewhat more nuanced view of extremely unusual cases in which algorithms or
even mathematical constants might conceivably be patentable in my view. [The
latter remarks occur near the end of a rather long lecture; I have highlighted
the relevant information, on page 324, for your convenience.]

Basically I remain convinced that the patent policy most fair and most suitable
for the world will regard mathematical ideas (such as algorithms) to be not
subject to proprietary patent rights. For example, it would be terrible if
somebody were to have a patent on an integer, like say 1009, so that nobody
would be able to use that number “with further technical effect” without paying
for a license. Although many software patents have unfortunately already been
granted in the past, I hope that this practice will not continue in future. If
Europe leads the way in this, I expect many Americans would want to emigrate so
that they could continue to innovate in peace.

Sincerely,

[signature]

Donald E Knuth

Professor of The Art of Computer Programming

STANFORD UNIVERSITY
STANFORD, CALIFORNIA 94305-2140

DONALD E. KNUTH

Professor Emeritus of The Art of Computer Programming

Department of Computer Science

[Telephone]

February 23, 1994

Commissioner of Patents and Trademarks

Box 4

Patent and Trademark Office

Washington, DC 20231

Dear Commissioner:

Along with many other computer scientists, I would like to ask you to
reconsider the current policy of giving patents for computational processes. I
find a considerable anxiety throughout the community of practicing computer
scientists that decisions by the patent courts and the Patent and Trademark
Office are making life much more difficult for programmers.

In the period 1945-1980, it was generally believed that patent law did not
pertain to software. However, it now appears that some people have received
patents for algorithms of practical importance–e.g., Lempel-Ziv compression
and RSA public key encryption–and are now legally preventing other programmers
from using those algorithms.

This is a serious change from the previous policy under which the computer
revolution became possible, and I fear this change will be harmful for society.
It certainly would have had profoundly negative effect on my own work: For
example, I developed software called TEX that is now used to produce more than
90% of all books and journals in mathematics and physics and to produce
hundreds of thousands of technical reports in all scientific disciplines. If
software patents had been commonplace in 1980, I would not have been able to
create such a system, nor would I probably have ever thought of doing it, nor
can I imagine anyone else doing so.

I am told that the courts are trying to make a distinction between mathematical
algorithms and nonmathematical algorithms. To a computer scientist, this makes
no sense, because every algorithm is as mathematical as anything could be. An
algorithm is an abstract concept unrelated to physical laws of the universe.

Nor is it possible to distinguish between “numerical” and “nonnumerical”
algorithms, as if numbers were somehow different from other kinds of precise
information. All data are numbers, and all numbers are data. Mathematicians
work much more with symbolic entities than with numbers.

To Commissioner of Patents and Trademarks - February 23, 1994 - Page 2

Therefore the idea of passing laws that say some kinds of algorithms belong to
mathematics and some do not strikes me as absurd as the 19th century attempts
of the Indiana legislature to pass a law that the ratio of a circle’s
circumference to its diameter is exactly 3, not approximately 3.1416. It’s like
the medieval church ruling that the sun revolves about the earth. Man-made laws
can be significantly helpful but not when they contradict fundamental truths.

Congress wisely decided long ago that mathematical things cannot be patented.
Surely nobody could apply mathematics if it were necessary to pay a license fee
whenever the theorem of Pythagoras is employed. The basic algorithmic ideas
that people are now rushing to patent are so fundamental, the result threatens
to be like what would happen if we allowed authors to have patents on
individual words and concepts. Novelists or journalists would be unable to
write stories unless their publishers had permission from the owners of the
words. Algorithms are exactly as basic to software as words are to writers,
because they are the fundamental building blocks needed to make interesting
products. What would happen if individual lawyers could patent their methods of
defense, or if Supreme Court justices could patent their precedents?

I realize that the patent courts try their best to serve society when they
formulate patent law. The Patent Office has fulfilled this mission admirably
with respect to aspects of technology that involve concrete laws of physics
rather than abstract laws of thought. I myself have a few patents on hardware
devices. But I strongly believe that the recent trend to patenting algorithms
is of benefit only to a very small number of attorneys and inventors, while it
is seriously harmful to the vast majority of people who want to do useful
things with computers.

When I think of the computer programs I require daily to get my own work done,
I cannot help but realize that none of them would exist today if software
patents had been prevalent in the 1960s and 1970s. Changing the rules now will
have the effect of freezing progress at essentially its current level. If
present trends continue, the only recourse available to the majority of
America’s brilliant software developers will be to give up software or to
emigrate. The U.S.A. will soon lose its dominant position.

Please do what you can to reverse this alarming trend. There are far better
ways to protect the intellectual property rights of software developers than to
take away their right to use fundamental building blocks.